Michael reported the segfault when kernel.kptr_restrict=2 is set. $ perf record ls ... perf: Segmentation fault Obtained 16 stack frames. ./perf(dump_stack+0x2d) [0x5068df] ./perf(sighandler_dump_stack+0x2d) [0x5069bf] ./perf() [0x43e47b] /lib64/libc.so.6(+0x3594f) [0x7f762004794f] /lib64/libc.so.6(strlen+0x26) [0x7f762009ef86] /lib64/libc.so.6(__strdup+0xd) [0x7f762009ecbd] ./perf(maps__set_kallsyms_ref_reloc_sym+0x4d) [0x51590f] ./perf(machine__create_kernel_maps+0x136) [0x50a7de] ./perf(perf_session__create_kernel_maps+0x2c) [0x510a81] ./perf(perf_session__new+0x13d) [0x510e23] ./perf() [0x43fd61] ./perf(cmd_record+0x704) [0x441823] ./perf() [0x4bc1a0] ./perf() [0x4bc40d] ./perf() [0x4bc55f] ./perf(main+0x2d5) [0x4bc939] Segmentation fault (core dumped)
The reason is that with kernel.kptr_restrict=2, we don't get the symbol from machine__get_running_kernel_start, which we want to use in maps__set_kallsyms_ref_reloc_sym and we crash. Check the symbol name value before calling maps__set_kallsyms_ref_reloc_sym and succeed without ref_reloc_sym being set. It's safe because we check its existence before we use it. Reported-by: Michael Petlan <[email protected]> Signed-off-by: Jiri Olsa <[email protected]> --- tools/perf/util/machine.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c index d7f31cb0a4cb..5de2b86b9880 100644 --- a/tools/perf/util/machine.c +++ b/tools/perf/util/machine.c @@ -1209,10 +1209,12 @@ int machine__create_kernel_maps(struct machine *machine) */ map_groups__fixup_end(&machine->kmaps); - if (machine__get_running_kernel_start(machine, &name, &addr)) { - } else if (maps__set_kallsyms_ref_reloc_sym(machine->vmlinux_maps, name, addr)) { - machine__destroy_kernel_maps(machine); - return -1; + if (!machine__get_running_kernel_start(machine, &name, &addr)) { + if (name && + maps__set_kallsyms_ref_reloc_sym(machine->vmlinux_maps, name, addr)) { + machine__destroy_kernel_maps(machine); + return -1; + } } return 0; -- 2.9.4
